Storytelling of a coin collection by means of RTI images: the case of the Simoneschi Collection in Palazzo Blu

Reflectance Transformation Imaging (RTI) is a technique that captures a subject's surface shape and color and enables the interactive re-lighting of the subject from any direction. Although at the beginning this technique was designed to aid Cultural Heritage specialists in the inspection and interpretation process, the recent advances of 3D web visualization platforms are increasing our capability to open this type of visual inspection to the ordinary public. Especially the methodologies for virtual manipulation of Cultural Heritage artifacts through RTI are gaining interest. In this context one of the most interesting kind of objects to acquire and virtually explore by means of RTI images are the ancient coins collections. Typically, a coin is a very small artwork, presented to the public from a distance and visible only from one side. Furthermore, coins have a lot of hidden knowledge that is difficult to transfer to the visitors in an easy, effective and understandable manner. What we present is the use of this new multimedia data, RTI images, in the process of digitalization and virtual presentation of the coin collection of the Palazzo Blu Museum (Pisa, Italy). The main goal of the project was to provide an improved access of ordinary people (visitors of the museum or web surfers) to the exposed numismatic materials. The result of this activity is an interactive kiosk that, integrated with the existing traditional museum exhibition, allows the visitors to interact and virtually explore every coin. The interactive presentation system, developed in HTML5 and designed to be deployed either by a museum kiosk or by a web site, is composed by a presentation section and the interactive viewer of the RTI images of each coin. The presentation part contains the description of the project and the organization of the coins into different subsets, using historical and thematic criteria, with the purpose to provide a presentation to a public of ordinary museum visitors. The RTI viewer offers a set of basic functionalities for the virtual manipulation of the coins using high-resolution images produced by RTI techniques. The RTI image of the coin, generated from a set of images acquired from the same point of view but with different lighting conditions, allows the visitor to change the direction of light in real time, making visible and appreciable details otherwise imperceptible. The virtual manipulation is completed by the free navigation on the coin, with basic operations like pan and zoom, and the possibility to flip the coin, to interact with the reverse, and to explore small areas of interest, identified by some hot spots on the surface and associated with text and pictures that provide additional information about the most interesting and important technical, historical and artistic features of the piece. The kiosk is currently installed inside the Museum Palazzo Blu in Pisa, in the exhibition room of the Ottavio Simoneschi's coin collection, and it will be soon loaded on the museum web site.